// Copyright 2014 BitPay Inc.
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://opensource.org/licenses/mit-license.php.

#include <univalue.h>
#include <univalue_utffilter.h>

#include <cstdint>
#include <cstdio>
#include <cstring>
#include <string>
#include <string_view>
#include <vector>

/*
 * According to stackexchange, the original json test suite wanted
 * to limit depth to 22.  Widely-deployed PHP bails at depth 512,
 * so we will follow PHP's lead, which should be more than sufficient
 * (further stackexchange comments indicate depth > 32 rarely occurs).
 */
static constexpr size_t MAX_JSON_DEPTH = 512;

static bool json_isdigit(int ch) {
    return ((ch >= '0') && (ch <= '9'));
}

// convert hexadecimal string to unsigned integer
static const char *hatoui(const char *first, const char *last,
                          unsigned int &out) {
    unsigned int result = 0;
    for (; first != last; ++first) {
        int digit;
        if (json_isdigit(*first)) {
            digit = *first - '0';
        } else if (*first >= 'a' && *first <= 'f') {
            digit = *first - 'a' + 10;
        } else if (*first >= 'A' && *first <= 'F') {
            digit = *first - 'A' + 10;
        } else {
            break;
        }

        result = 16 * result + digit;
    }
    out = result;

    return first;
}

enum jtokentype getJsonToken(std::string &tokenVal, unsigned int &consumed,
                             const char *raw, const char *end) {
    tokenVal.clear();
    consumed = 0;

    const char *rawStart = raw;

    // skip whitespace
    while (raw < end && (json_isspace(*raw))) {
        raw++;
    }

    if (raw >= end) {
        return JTOK_NONE;
    }

    switch (*raw) {
        case '{':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_OBJ_OPEN;
        case '}':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_OBJ_CLOSE;
        case '[':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_ARR_OPEN;
        case ']':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_ARR_CLOSE;

        case ':':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_COLON;
        case ',':
            raw++;
            consumed = (raw - rawStart);
            return JTOK_COMMA;

        case 'n':
        case 't':
        case 'f':
            if (!strncmp(raw, "null", 4)) {
                raw += 4;
                consumed = (raw - rawStart);
                return JTOK_KW_NULL;
            } else if (!strncmp(raw, "true", 4)) {
                raw += 4;
                consumed = (raw - rawStart);
                return JTOK_KW_TRUE;
            } else if (!strncmp(raw, "false", 5)) {
                raw += 5;
                consumed = (raw - rawStart);
                return JTOK_KW_FALSE;
            } else {
                return JTOK_ERR;
            }

        case '-':
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9': {
            // part 1: int
            std::string numStr;

            const char *first = raw;

            const char *firstDigit = first;
            if (!json_isdigit(*firstDigit)) {
                firstDigit++;
            }
            if ((*firstDigit == '0') && json_isdigit(firstDigit[1])) {
                return JTOK_ERR;
            }

            // copy first char
            numStr += *raw;
            raw++;

            if ((*first == '-') && (raw < end) && (!json_isdigit(*raw))) {
                return JTOK_ERR;
            }

            // copy digits
            while (raw < end && json_isdigit(*raw)) {
                numStr += *raw;
                raw++;
            }

            // part 2: frac
            if (raw < end && *raw == '.') {
                // copy .
                numStr += *raw;
                raw++;

                if (raw >= end || !json_isdigit(*raw)) {
                    return JTOK_ERR;
                }
                // copy digits
                while (raw < end && json_isdigit(*raw)) {
                    numStr += *raw;
                    raw++;
                }
            }

            // part 3: exp
            if (raw < end && (*raw == 'e' || *raw == 'E')) {
                numStr += *raw; // copy E
                raw++;

                if (raw < end && (*raw == '-' || *raw == '+')) { // copy +/-
                    numStr += *raw;
                    raw++;
                }

                if (raw >= end || !json_isdigit(*raw)) {
                    return JTOK_ERR;
                }
                // copy digits
                while (raw < end && json_isdigit(*raw)) {
                    numStr += *raw;
                    raw++;
                }
            }

            tokenVal = numStr;
            consumed = (raw - rawStart);
            return JTOK_NUMBER;
        }

        case '"': {
            // skip "
            raw++;

            std::string valStr;
            JSONUTF8StringFilter writer(valStr);

            while (true) {
                if (raw >= end || (uint8_t)*raw < 0x20) {
                    return JTOK_ERR;
                } else if (*raw == '\\') {
                    // skip backslash
                    raw++;
                    if (raw >= end) {
                        return JTOK_ERR;
                    }

                    switch (*raw) {
                        case '"':
                            writer.push_back('\"');
                            break;
                        case '\\':
                            writer.push_back('\\');
                            break;
                        case '/':
                            writer.push_back('/');
                            break;
                        case 'b':
                            writer.push_back('\b');
                            break;
                        case 'f':
                            writer.push_back('\f');
                            break;
                        case 'n':
                            writer.push_back('\n');
                            break;
                        case 'r':
                            writer.push_back('\r');
                            break;
                        case 't':
                            writer.push_back('\t');
                            break;

                        case 'u': {
                            unsigned int codepoint;
                            if (raw + 1 + 4 >= end ||
                                hatoui(raw + 1, raw + 1 + 4, codepoint) !=
                                    raw + 1 + 4) {
                                return JTOK_ERR;
                            }
                            writer.push_back_u(codepoint);
                            raw += 4;
                            break;
                        }
                        default:
                            return JTOK_ERR;
                    }

                    // skip esc'd char
                    raw++;
                } else if (*raw == '"') {
                    // skip "
                    raw++;
                    // stop scanning
                    break;
                } else {
                    writer.push_back(static_cast<uint8_t>(*raw));
                    raw++;
                }
            }

            if (!writer.finalize()) {
                return JTOK_ERR;
            }
            tokenVal = valStr;
            consumed = (raw - rawStart);
            return JTOK_STRING;
        }

        default:
            return JTOK_ERR;
    }
}

enum expect_bits : unsigned {
    EXP_OBJ_NAME = (1U << 0),
    EXP_COLON = (1U << 1),
    EXP_ARR_VALUE = (1U << 2),
    EXP_VALUE = (1U << 3),
    EXP_NOT_VALUE = (1U << 4),
};

#define expect(bit) (expectMask & (EXP_##bit))
#define setExpect(bit) (expectMask |= EXP_##bit)
#define clearExpect(bit) (expectMask &= ~EXP_##bit)

bool UniValue::read(std::string_view str_in) {
    clear();

    uint32_t expectMask = 0;
    std::vector<UniValue *> stack;

    std::string tokenVal;
    unsigned int consumed;
    enum jtokentype tok = JTOK_NONE;
    enum jtokentype last_tok = JTOK_NONE;
    const char *raw{str_in.data()};
    const char *end{raw + str_in.size()};
    do {
        last_tok = tok;

        tok = getJsonToken(tokenVal, consumed, raw, end);
        if (tok == JTOK_NONE || tok == JTOK_ERR) {
            goto return_fail;
        }
        raw += consumed;

        bool isValueOpen = jsonTokenIsValue(tok) || tok == JTOK_OBJ_OPEN ||
                           tok == JTOK_ARR_OPEN;

        if (expect(VALUE)) {
            if (!isValueOpen) {
                goto return_fail;
            }
            clearExpect(VALUE);
        } else if (expect(ARR_VALUE)) {
            bool isArrValue = isValueOpen || (tok == JTOK_ARR_CLOSE);
            if (!isArrValue) {
                goto return_fail;
            }

            clearExpect(ARR_VALUE);
        } else if (expect(OBJ_NAME)) {
            bool isObjName = (tok == JTOK_OBJ_CLOSE || tok == JTOK_STRING);
            if (!isObjName) {
                goto return_fail;
            }
        } else if (expect(COLON)) {
            if (tok != JTOK_COLON) {
                goto return_fail;
            }
            clearExpect(COLON);
        } else if (!expect(COLON) && (tok == JTOK_COLON)) {
            goto return_fail;
        }

        if (expect(NOT_VALUE)) {
            if (isValueOpen) {
                goto return_fail;
            }
            clearExpect(NOT_VALUE);
        }

        switch (tok) {
            case JTOK_OBJ_OPEN:
            case JTOK_ARR_OPEN: {
                VType utyp = (tok == JTOK_OBJ_OPEN ? VOBJ : VARR);
                if (!stack.size()) {
                    if (utyp == VOBJ) {
                        setObject();
                    } else {
                        setArray();
                    }
                    stack.push_back(this);
                } else {
                    UniValue tmpVal(utyp);
                    UniValue *top = stack.back();
                    top->values.push_back(tmpVal);

                    UniValue *newTop = &(top->values.back());
                    stack.push_back(newTop);
                }

                if (stack.size() > MAX_JSON_DEPTH) {
                    goto return_fail;
                }

                if (utyp == VOBJ) {
                    setExpect(OBJ_NAME);
                } else {
                    setExpect(ARR_VALUE);
                }
                break;
            }

            case JTOK_OBJ_CLOSE:
            case JTOK_ARR_CLOSE: {
                if (!stack.size() || (last_tok == JTOK_COMMA)) {
                    goto return_fail;
                }

                VType utyp = (tok == JTOK_OBJ_CLOSE ? VOBJ : VARR);
                UniValue *top = stack.back();
                if (utyp != top->getType()) {
                    goto return_fail;
                }

                stack.pop_back();
                clearExpect(OBJ_NAME);
                setExpect(NOT_VALUE);
                break;
            }

            case JTOK_COLON: {
                if (!stack.size()) {
                    goto return_fail;
                }

                UniValue *top = stack.back();
                if (top->getType() != VOBJ) {
                    goto return_fail;
                }

                setExpect(VALUE);
                break;
            }

            case JTOK_COMMA: {
                if (!stack.size() || (last_tok == JTOK_COMMA) ||
                    (last_tok == JTOK_ARR_OPEN)) {
                    goto return_fail;
                }

                UniValue *top = stack.back();
                if (top->getType() == VOBJ) {
                    setExpect(OBJ_NAME);
                } else {
                    setExpect(ARR_VALUE);
                }
                break;
            }

            case JTOK_KW_NULL:
            case JTOK_KW_TRUE:
            case JTOK_KW_FALSE: {
                UniValue tmpVal;
                switch (tok) {
                    case JTOK_KW_NULL:
                        // do nothing more
                        break;
                    case JTOK_KW_TRUE:
                        tmpVal.setBool(true);
                        break;
                    case JTOK_KW_FALSE:
                        tmpVal.setBool(false);
                        break;
                    default:
                        /* impossible */
                        break;
                }

                if (!stack.size()) {
                    *this = tmpVal;
                    break;
                }

                UniValue *top = stack.back();
                top->values.push_back(tmpVal);

                setExpect(NOT_VALUE);
                break;
            }

            case JTOK_NUMBER: {
                UniValue tmpVal(VNUM, tokenVal);
                if (!stack.size()) {
                    *this = tmpVal;
                    break;
                }

                UniValue *top = stack.back();
                top->values.push_back(tmpVal);

                setExpect(NOT_VALUE);
                break;
            }

            case JTOK_STRING: {
                if (expect(OBJ_NAME)) {
                    UniValue *top = stack.back();
                    top->keys.push_back(tokenVal);
                    clearExpect(OBJ_NAME);
                    setExpect(COLON);
                } else {
                    UniValue tmpVal(VSTR, tokenVal);
                    if (!stack.size()) {
                        *this = tmpVal;
                        break;
                    }
                    UniValue *top = stack.back();
                    top->values.push_back(tmpVal);
                }

                setExpect(NOT_VALUE);
                break;
            }

            default:
                goto return_fail;
        }
    } while (!stack.empty());

    /* Check that nothing follows the initial construct (parsed above).  */
    tok = getJsonToken(tokenVal, consumed, raw, end);
    if (tok != JTOK_NONE) {
        goto return_fail;
    }

    return true;

return_fail:
    clear();
    return false;
}
